1. Technical Field
The presents invention relates to a spatial light modulator and an image display device, and particularly to a liquid crystal type spatial light modulator.
2. Related Art
A spatial light modulator, particularly a liquid crystal type spatial light modulator is equipped with various kinds of wires such as data lines, scan lines, capacitance lines, etc. and various kinds of electric elements such as thin film transistors (hereinafter referred to TFT (Thin Film Transistor)), thin film diodes, etc. in an image display area. Therefore, in each area, an area where light actually-contributing to display is transmitted or reflected (i.e., an opening area of each pixel) is limited by existence of various kinds of wires, electric elements, etc. in each pixel. Here, the aperture ratio of each pixel is defined as the rate of the aperture area (in which light actually-contributing to display is transmitted or reflected) to the overall area of each pixel. The aperture ratio of each pixel is set equal to about 70%, for example. For example, light incident from a light source portion to a spatial light modulator is substantially collimated light, and the light amount corresponding to the aperture ratio of each pixel out of the overall light amount of light incident to the spatial light modulator is effectively modulated.
Therefore, a microlens array having a plurality of microlenses each of which corresponds to each pixel is formed on a counter substrate. The microlens has a function of condensing light traveling to a non-opening area on a pixel basis. Here, the non-opening area is an area which is located around an opening area and where wires, etc. as described above exist. Light condensed by each microlens is guided into the opening area of each pixel while transmitted through a liquid crystal layer of the spatial light modulator.
For example, Japanese Patent Application Publication 2004-70282 (JP-A-2004-70282) has proposed that a microlens array is applied to a spatial light modulator.
Most of light incident to a microlens is emitted from the microlens with the intersecting angle (light beam angle) between the light beam and the optical axis being kept large by the condensing action of the microlens. The liquid crystal layer of the spatial light modulator can display an image with higher contrast as light having a smaller light beam angle is incident to the liquid crystal layer. Therefore, when the amount of light having a large light beam angle is increased, the contrast of the image is lowered. Furthermore, a projection optical system transmits therethrough only light having the incident angle corresponding to a numerical aperture thereof (hereinafter referred to as “NA”). As described above, in the spatial light modulator using the microlens array, light is condensed to the opening area at a predetermined NA by each microlense. The light incident to the opening area is modulated in accordance with an image signal in the liquid crystal portion, for example, and then the light thus modulated is emitted from the liquid crystal portion at a predetermined NA which is substantially equal to that for the incident light.
With respect to the light emitted from the spatial light modulator, the light beam angle between the optical axis and the light beam refracted by the condensing action of the microlens is increased. Light having a light beam angle larger than NA of the projection optical system is shut off by the projection optical system. If the amount of light having a light beam angle larger than NA of the projection optical system is large, a large amount of light is shut off by the projection optical system, and thus the light using efficiency is lowered. With respect to the spatial light modulator using the microlens array, as described above, even when light from the light source portion is efficiently guided to the opening area, the amount of light having a large light beam angle is increased, so that the contrast is lowered and the light using efficiency is lowered.